SDLC vs STLC – Key Differences Explained

There are numerous development life cycles that have been developed in order to achieve different required objectives of an organization. These life cycles range from lightweight and fast methodologies, where time to market is of the essence, to fully controlled and documented methodologies where quality and reliability are key drivers. Each of these methodologies plays a key role in software development and the most appropriate development process should be applied to each project. 

The models specify the various stage of the process and the order in which they are carried out. Any software product delivery goes through two major life cycles that are Software Development Life Cycle (SDLC) and Software Testing Life Cycle(STLC). Let’s discuss in this article the key differences between SDLC Vs STLC and the role they play in complete software product delivery.

SDLC vs STLC – Definition Difference

What is SDLC?

Any product or system development requires a set of procedures, which mainly depend on the project aims and goals. This procedure is the Software Development Life Cycle (SDLC). “Software Development Life Cycle(SDLC) is a process of creating or altering systems and the models and methodologies that people use to develop these systems or products”.

Any Software Development Life Cycle (SDLC), that we adopt for our organization, should result in high quality system that meets or exceeds customer expectations, reaches completion within time frame and cost estimates, works effectively and efficiently.

Read here- all about SDLC Model

What is STLC?

The software development life cycle model that is adopted for any software project will have big impact on the testing process. Testing does not exist in isolation, test activities are highly related to software development activities. For example, if time to market is key driver, then the testing must be fast and efficient. Another example is for an e-commerce application, the testing process should be more focused on performance and scalability. 

Testing process itself includes various testing activities and phases, all these testing phases are collectively named as Software Testing Life Cycle(STLC).

Read all about STLC in Software Testing

Different Phases of SDLC vs STLC:

SDLC or STLC is not a methodology per se, but rather a description of the phases that a methodology should address to build and deliver the product or systems. Any software development life cycle or software testing life cycles is composed of distinct work phases that are used by software engineers, different stakeholders etc.

Let’s discuss these phases involved in each life cycle. 

Different phases of SDLC:

1. Initiation:

Initiation phase begins when a sponsor(a person who will own the project) identifies a need or an opportunity. A Proposal is created in this phase.

2. System Concept Development:

This phase defines the scope or boundary of the concept. Includes Systems Boundary Document, Cost Benefit

Analysis, Risk Management, Plan and Feasibility Study.

3. Planning:

In planning phase, usually, development of a Project Management Plan and other planning documents happens which provides the basis for acquiring the resources needed to achieve a solution. 

4. Requirements Analysis:

In requirements analysis phase, usually Business analysts and Product analysts gather the requirements achieved from above phases. Then they analyse user needs and develop user requirements and create a detailed Functional Requirements Document. Usually in this phase, the business requirements get converted in to software language.

A requirement management tool helps in requirements analysis phase, such as this tool supports the recording of requirements, requirement attributes(e.g. Priority, person responsible for the task) and annotation and facilitates traceability through layers of requirements and requirements change management. Some requirement management tools also provide facilities for static analysis such as consistency checking and violations to pre-defined requirements rules. 

Visure Solutions, Inc., Jira, Xebrio, Aha!, Jama Software etc are few examples of requirement management tools. 

5. Design: 

In the design phase, architecture and senior developers come into play. They go through the business requirement output and transform detailed requirements into complete, detailed System Design.

The system design mainly focuses on how to deliver required functionality.

On a high level there are two stages in design phase.

i. HLD – High Level Design

ii. LLD – Low Level Design

1. HLD – High Level Design: 

High level design phase gives the high-level architecture of the software product to be developed and is done by architects and senior developers.

2.  LLD – Low Level Design

Low Level Design phase describes how each and every feature in the product should work and how every component should work. Here, it is done by senior developers.

In the design phase only the design is created, coding is not a part of this phase.

6. Development: 

In this phase, software developers convert a design into complete information system. This phase includes acquiring and installing system environment, creating and testing data bases, preparing test case procedures, preparing test files, coding, compiling, refining programs, performing test readiness, review and procurement activities.  

This is the phase where we start building the software and start writing the code for the product.

Here, different programming languages such as Java, Python, C++ etc. can be used in order to develop a product based on the organization.

7. Integration and Test:

This phase is meant to check that developed system conforms to requirements as specified in the functional requirements document.

Testing process is conducted by software testing engineers. In this phase software testers perform a thorough testing of the product and produce test analysis reports based on it.

There are various types of testing that software testers perform based on the project/product requirement such as manual testing, automation testing, performance testing, security testing, ETL testing etc. After the testing is done, the testers also updates the Requirement Traceability Matrix document with the test cases, bugs details etc.

Different tools are used for each testing type for example, Testsigma is a tool which lets you automate your tests for web, mobile, APIs and desktop from the same place, thus, you don’t to have to use different tools for different platforms. – Try Testsigma Tool

8. Implementation:

In this phase, only the code already developed by the developers and tested by the testers goes to the production for further use by customers/end-users. 

In production implementation phase different team members gets involved such as testers for doing one round of sanity or confidence testing to confirm the software is working as expected in production environment. 

If any bug is raised in the production environment during  implementation phase, testers again raise a bug and it goes via production hot fix depending on the priority and severity of the issue/bug.

9. Operations and Maintenance:

This phase describes tasks to operate and maintain the implemented/deployed software or information systems in a production environment.This includes Post-Implementation and In-Process Reviews.

In this phase also, some time, the customers use the product and if they find any bugs and defects, they are reported and fixed. 

10. Disposition:

This phase describes the end-of-system activities.All the closure activities happens in this phase. The emphasis is given to proper preservation of data that is a thorough retrospective of the all the activities done during SDLC life cyle happens, updating and keeping the test reports, documents, environments etc happens for future re-use purpose.

Different Phases of STLC:

1. Requirement Analysis:

Requirement analysis stage is the beginning stage of software testing life cycle. In this stage, the quality assurance professionals (testers) go through the Requirements Documents created by Business analysts and/or Product analysts and identify the testing requirements.

The senior quality assurance engineers gets involved in various requirement discussion meetings along with technical architecture, business analysts, product owner, clients and various other stackholders. This helps them to understand the requirements in-depth, so that they can segregate the testing further into various types of testing such as functional tests, non-function tests(such as performance test, security test etc). 

At this stage, a requirement traceability matrix(RTM) document is also created by the testers. RTM document is a testing document or an artifact that maps requirements to corresponding test cases. 

To know more about RTM you can also refer: Requirement Traceability Matrix(RTM) in Regression Testing

2. Planning And Control:

During test planning testers and other stakeholders make sure they understand the goals and objective, and the risks which testing is intended to address. Based on this understanding, they derive an approach and plan for the tests, including specification of test activities.

A test plan is created at this stage. A test plan is a document describing the scope, approach, resources and schedule of intended test activities. It identifies, among others, test items, the features to be tested, the testing tasks, who will do each tasks, degree of tester independence, the test environment, the test design techniques and entry and exit criteria to be used. It is a record of test planning process.

Test planning stage has following major tasks:

1. Determine the scope of the testing, risks present and identify the objectives of testing.
2. Determine the test approach such as which testing techniques to use, test items, coverage, what needs to be tested and how.
3. Implement the test policy and/or the test strategy.
4. Determine the required test resources (e.g. people, test environment, PCs etc.)
5. Schedule test analysis and design tasks, test implementation, execution and evaluation.
6. Determine the exit criteria: we need to set the exit criteria such that they will show us which tasks and checks we must complete for a particular level of testing before we can say that testing is finished.

A very good in-depth analysis on entry and exit criteria in STLC is given here.

Test control is an ongoing activity that plays throughout the STLC life cycle. Test control is a test management task that deals with developing and applying set of corrective actions to get a test project on track when monitoring shows a deviation from what was planned. Test monitoring is a management task that deals with the activities related to periodically checking the status of a test project. Test reports are prepared to compare the actual status to that which was planned. Read here about Test Monitoring and Test Control

3. Analysis And Design:

Test analysis and design is the activity where general testing objectives are transformed into tangible test conditions and test designs. Test analysis and design has the following major tasks:

1. Review the test basis that is the product risk analysis, requirements, architecture, design specifications, interfaces, etc. Testers can start designing black box testing before the code exists.
   
2. Evaluate the testability of the test basis. Such as, check that the requirement is written in a way that allows a tester to design tests for example if the performance of the software is important, that should be specified in a testable way such as the software needs to respond with in 5 seconds when 20 people logged on.
   
3. Identify and prioritize test conditions to provide the tester a high level list of what are the area that needs to be tested. 

4. Design and prioritize the tests. Once we identified the tests conditions and designed the tests we need to identify the data which will be used to execute the test cases and test procedures.

5. Design the test environment setup and identify any required infrastructures and tools.

6. Test environments, Test scripts etc should be designed in such a way that it can be reused for future similar testing tasks. This will help in reducing the effort and cost. 

One way to achieve this is automating the manual test cases. Whenever we need to execute or test similar set of functionality or task, we can trigger the automation which eliminates the manual effort, the tests will be run more than once and shall able to check the results quickly and easily. 

Testsigma is one of the automation tool where you can build stable and reliable automated tests rapidly without complex setups, integrations or development effort.

Automate your tests for web, mobile, desktop and APIs, and integrate them seamlessly within your STLC with Testsigma

4. Implementation And Execution:

During test implementation and execution, we take the test conditions and make them into test cases and testware and setup the environment.

1. Implementation: Develop and prioritize your test cases using the different testing techniques such as boundary value analysis, equivalent partition etc and create those test cases. We also need to automate the manual test cases using different automation test tools such as Testsigma, which is a cloud based, AI-driven test automation platform that helps you automate your web application testing, mobile application testing , and APIs from the same place with ease of writing the test cases in simple English.

2. Execution: Execute test suites and individual test cases. This could be manually done or by executing automation scripts.

Logging of the outcome of test execution can also include:

• images
• videos 
• the identities and versions of the software under test, tools etc

Also, reporting of the defects in the form of defect tickets (bug) which should have all the information – when and in what condition the bug is found, the associated logs, failure images or recording of the bug etc. 

Once the bug fix happens, testers needs to re-execute the same tests(confirmation testing or re-testing) in order to confirm that the fix is working and now the actual result matches the expected result.

5. Evaluation Exit Criteria And Reporting:

Evaluating exit criteria gives us the information on whether we can declare a given testing activity as completed or not. 

Evaluating exit criteria has the following major tasks:

1. Check the test logs against the exit criteria specified during test planning phase.
   
2. Assess if more tests are needed or if the exit criteria specified should be changed.
   
3. Write test summary report for stakeholders. Test summary report is a  document summarizing testing activities and results. It also contains an evaluation of the corresponding test items against exit criteria.

6. Test Closure Activities:

During test closure activities, we collect data from completed test activities to consolidate experience, including checking and filling Testware, and analysing facts and numbers. Usually this is done when software is delivered.

Testware is the artifacts produced during the test process required to plan, design, and execute tests, such as documentation, scripts, inputs expected results, actual results, set-up and clear-up procedures, files, data bases, environment, and any additional software utilities used in testing.

Test closure activities include the following major tasks:

1. Check which planned deliverables we actually delivered and ensure all incident reports have been resolved through defect repair or deferral.
   
2. We document the acceptance or rejection of the software system.
   
3. Finalize and archive testware, such as scripts, the test environments and any other test infrastructures for future reuse purpose.
   
4. Handover testware to the maintenance team who will support the software and make any maintenance changes or fixes required if any.
   
5. Retrospective activities take place in-order to evaluate how the testing went and analyse lessons learned for future releases. This might include process improvements for the software development life cycle or software testing life cycle etc. These are also documented in a test summary report or might be part of an overall project evaluation report.

Why should We Adopt Software Development Life Cycle(SDLC) and What are the Key Features of it?

From the above discussion on different phases of SDLC, you might be clear now that SDLC is the process of planning, creating, testing and deploying. While there are countless advantages of having this structure for a design project, here are the most common ones:

1. It clarifies the goal of the software project, so that the plan is implemented with precision and relevance.
2. Products can be properly tested before delivery, also we mitigate the incidents/bugs timely. The early detection of bugs is necessary to minimize the cost of bug fixing.
3. The SDLC gives you a well-structured documentation of the entire project execution,  including a complete records of everything that occurs. So that if any key project members leaves and a new member has to pick up the task, it becomes easier for them. 
4. The project manager can properly manage a project if deliverables are completed on time and within the budget. 
5. SDLC model provides the project with flexibility to loop around, take the feedback during any stages of the life cycle. It’s the best way to ensure optimal control, minimize problems, and allow the project manager to deliver the product more efficiently at the given time frame.

Why Software Testing Life Cycle(STLC) We should Adopt and What are the Key Features of it?

. Few of the common reason why we should adopt the Software Testing Life Cycle in software projects are:

1. Adopting a proper Software Testing Life cycle involves testers in requirement reviews and user story refinement etc phases which ensures identification of some of the requirement defects even before their implementation. It significantly reduces the fixing cost.
   
2. Identify the defects early: Developing any applications can leave room for errors which could lead to difference in actual behaviour of the software from expected behaviour of the software. Any bug in the early phases, fixing them costs a less amount of money and time as compared to if it was found during the later stage of the software development life cycle.
   
3. Quality of the software product: STLC ensures the developed product meets the specification of the user requirement as per the promise via its all phases starting from Test Planning and Control phase to closure activities. 

4. When testers work closely with developers, regular test control and test management happens, it enhances testers understanding of each part of the code, and all the stake holders of that software projects remain in the same page where the software product is now, which further enables testers to do more efficient testing against customer requirements. 

5. Customer is satisfied as software testing life cycle helps test that software meets the requirement as per the user and provide a perfect user experience whether in terms of functionality, look and feel, security, or scalability.

What is the difference between SDLC & STLC (SDLC vs STLC) ?

Ser.No.	Feature	SDLC	STLC
1.	Stands for	SDLC stands for Software Development Life Cycle	STLC stands for Software Testing Life Cycle.
2.	Definition	Software Development Life Cycle(SDLC) is a process of creating or altering systems and the models and methodologies that people use to develop these systems or products.	Software testing is the act of examining the artifacts and the behaviour of the software under test by validation and verification.
3.	Purpose/Goal	Main purpose of SDLC is to provide a structured and organized approach for the development of software. Goal is to ensure that the software is developed in a way that meets the requirements of the customer, is of high quality, and is delivered on time and within budget.	The main objective or goal of the STLC is to identify and document any defects or issues in the software application as early as possible in the development process.
4.	Focus	SDLC focuses on both development and testing phases.	STLC focuses on only Testing phases.
5.	Phases	SDLC mainly has 9 different phases those are   Initiation System Concept Development Planning Requirements Analysis Design Development Implementation Operations and Maintenance Disposition	STLC consist overall 5 different phases those are: RequirementsAnalysisPlanning and ControlAnalysis and DesignImplementation and ExecutionEvaluation exit criteria and reportingTest Closure activities
6.	Requirement Gathering Phase	Business analyst gathers the requirements and create the complete product development Plan	QA team analyses requirement documents and creates the testing plan of the software product.
7.	Design Phase	Based on the requirement document created during requirement phase, the development team and architecture build High level design and Low level design document.	Test Architect and Testing Lead or team usually plan the test strategy during the analysis and design phase.
8.	Development phase/Implementation Phase.	During the development phase of SDLC lifecycle developers develop the codes.	During the Implementation phase, the testers develop and prioritize test cases using the different testing techniques, setup the test environments etc.
9.	Testing	Developers perform the unit testing, integration testing for their code. Fix the reported bugs.	Tester performs the actual testing and reports the bug and do the retesting of the bug fixes.
10.	Deployment or Maintenance Phase	Development team supports the product release activities and fixing of any production issues found with respect to their code.	The QA team executes the production sanity and regression suites to check the code deployed is working fine and no bugs are there.
11.	Objectives	The objective of different phases of SDLC life cycle is to overcome any hurdle on the way to successful software development of the product.	The objective of different phases of STLC life cycle is to find out any drawbacks or incidents/bugs present in the software.
12.	Outcome	The end result of SDLC is a good quality product gets delivered to the customer.	The outcome of STLC is ideally to deliver a defect free software.

Summary

The ultimate goal that we want to achieve by following the Software Development Life Cycle and Software Testing Life Cycle is that the software meets requirements, to demonstrate that the system is fit for purpose it was built for. Organization should adopt both the SDLC and STLC life cycle. Doing so enables them to come up with an end result that perfectly suits their particular needs and situation.

These lifecycles provide teams with the highest level of documentation and management control. All the stake holders, users/customers and team involved agree on the objective upfront and come up with a clear action plan for achieving that goal. Each stakeholder also understands the resources and costs required, hence chances of delivering of a high quality product is guarantee. 

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Frequently Asked Questions

Is STLC a part of SDLC?

Yes, STLC  (Software Testing Life Cycle) is an integral part of SDLC (Software Development Life Cycle). Different activities performed during STLC phases help towards the outcome and objective of SDLC life cycle i.e delivering a high quality and bug free system to the customer which meets their requirement. 

Which is better SDLC or STLC?

Since both Software development life cycle and Software testing life cycle are primarily focused on same objective that is delivering a high quality, bug free software on time to the customer, both play vital role in developing a software products. SDLC and STLC are dependent on each other, and always stands together when it comes to software product development.